Raman analysis is a well-known analytical technique used for structural analysis of molecular species. Raman analysis exploits the inelastic scattering of light by a substance that carries information about the vibrational spectrum of the constituent molecular compounds. The distinguishing feature of Raman analysis compared with, for example, infrared (IR) or near infrared (NIR) absorption vibrational spectroscopy is the fact that the optical excitation of the sample is done at a much shorter wavelength of light and the corresponding Raman signal is emitted in the spectral band of a much shorter wavelength than the IR absorption lines of the same sample. This feature allows efficient analysis of aqueous solutions and also makes it possible to construct very compact instruments.
Typical Raman systems employed so far use a monochromatic source of incident radiation such as a laser combined with a spectrometer and a detection system such as a CCD camera (dispersive Raman). Another type of a conventionally used Raman system is Fourier transform Raman that uses a scanning interferometer and a single detector for spectral analysis. Lasers that are used for Raman analysis typically emit in the visible, near infrared, or near ultraviolet spectrum. Many variations of radiation detectors have been used in the art, ranging from photomultiplier tubes to CCD cameras.
Traditionally, the cost of Raman spectrometers has been driven by the cost of the laser excitation source, the spectrometer that may use notch filters designed to suppress Rayleigh scattering, cooled CCD camera and the signal analysis module that usually requires a fully functional computer, operating system and specialized software. Some Raman systems also employ a fiber-optic probe for delivering laser light to the sample and collecting the Raman signal.